A prospective study of an instrument to predict progression of ischemic strokes is proposed. The predictor is based on six patient characteristics that are: history of decreased consciousness at stroke onset, systolic blood pressure on admission, weakness on examination, blood glucose, size of the lesion on the first CT after stroke and the presence of moderate or severe edema or mass effect. Progression of ischemic stroke is defined as neurological worsening between two examinations that reflects changes in the same arterial distribution as the original infarction or is due to mass effect and not due to medical, angiographic or surgical complications. Fifteen percent of ischemic stroke patients will progress in hospital in the first 21 days after onset. Patients who progress are more likely to die or be disabled. There is no means available to prevent or successfully treat this common condition. All patients who are hospitalized with ischemic stroke in either of two hospitals will be examined and followed daily to find progression. Special efforts will be made to see patients in the first few hours after stroke and look at changes in patient characteristics over time related to circadian rhythm and associate these with progression. Data will be collected about the history, examination and results of diagnostic tests including brain imaging, angiography, carotid duplex and transcranial Doppler. When patients progress, data will be collected about relevant repeated tests. Comparison will be made by group on the observed and expected rate of progression for patients seen early after their stroke and using more complete data and newly available tests. New predictors will be developed by univariate analysis and multivariate regression analysis. Efforts will be made to find the likeliest mechanism of progression in each case.